Pressure-sensitive adhesive tape



May 17,?"1'960 c, BARTELL, ETAL 2,937,109

PRESSURE-SENSITIVE ADHESIVE TAPE Filed May 7, 1956 /MPREGNATED BACKING.

PAPan MPRIENATED W 'H C-Hl-OIQPIMI Anna An Ann-Acorn. Aen'a INVENTORE) 771W, M 3% m a ATTORNEYS 2,937,109 PRESSURE-SENSITIVE annnsrvn TAPE Charles Bartel], New Brunswick, Charles L. Weidner,

Cranbury, and Richard M. Smith, Nixon, N.J., assignors, by mesne' assignments, to Johnson & Johnson,

New Brunswick,'NJ., a corporation of New Jersey Application May 1, 1956, Serial No. ss3,19s 3 Claims. (Cl.117-122) This invention relates to a normally tacky and pressure-sensitive adhesive sheet material and, -,more particularly, to a normally tacky and pressure-sensitivetape formed with a unified paper backing impregnated with a chloroprene polymer.

Paper-backed, normally tacky and pressure-sensitive adhesive tapes, particularly those used for masking purposes, should have high elongation, good flexibility, high edge tear, good tensile strength and adequate internal strength to prevent delamination of the backing upon unrolling of the tape. In the case of masking tapes, the product must have high elongation, flexibility and edge tear in order that the tape be curved to mask curved lines without tearing during application. The delamination resistance, or resistanceof the backing to being split into two layers by forces perpendicular to the sheet, is neces"-. sary to enable unwinding of the tape and removal from the surface after it has served its intended function; j

Paper backings for use in pressure-sensitive tapes can be unified or strengthened internally by treatment of the paper with aqueous latices of elastomeric polymers; The sheets are impregnated in amount suflicient to de-' posit substantial rubbery polymer solids in the web to bond the fibers thereof to a degree sufficient to lend the tape high internal strength. In the treatment of paper webs with latices, however, it has been generally found that the edge tear, elongation and flexibility of the sheet suffered considerably whenever ingredients were incorporated in the latex for the purpose of increasing the tensile strength and delamination resistance of the product. Obviously, a balancing of the characteristics of the tape is necessary to obtain a successful commercial prod net and increasing one property to the severe detriment of others is not advantageous. Another consideration is that the elastomeric polymer in unifying the paper must not cause a detrimental change in the appearance of the paper such as by effecting a discoloration thereof- Accordingly, it is an object of this invention to provide a unified paper web suitable for use as a backing element for a normally tacky and pressure-sensitive adhesive sheet wherein the backing has the characteristics mally tacky and pressure-sensitive paper tape having the aforementioned characteristics.

These and other objects of the invention will become apparent when consideration is given to the hereinafter detailed description of the invention.

In accordance with this invention an open, porous saturable paper web is treated with an aqueous dispersion of a chloroprene polymeric elastomer to unify the paper in imparting satisfactory elongation, tensile strength and delamination resistance. It has been found that chloroprene polymeric elastomers are excellent unifying agents for this purpose. It has been further found, however, that such chloroprene polymers on aging cause a discoloration and embrittlement of the paper. While not be ing bound by any theory of action, the chloroprene polymer on aging appears to release HCl which attacks the paper tenderizing .it and causing the paper to become brittle and crumbly. Moreover, the paper is discolored toan extent to render it commercially unattractive.

It has been found, however, that a chloroprene polymeric elastomer may be used successfully as a paper unifying agent if there is used in conjunction therewith a small amount of a compound which is a derivative of ammonia and commonly'called an aminoacetic acid.'

The aminoacetic acids useful in accordance with this invention are derivatives of ammonia wherein at least one and preferably more than one. of the hydrogensin ammonia is replaced by a group having the methyl carboxy radical, their salts and ethers. One hydrogen may also be replaced by an alkyl amine or by a compound having an alkyl amine methyl carboxy radical and preferably having two methyl carboxy radicals. Also, one or more hydrogens may be replaced by ethylol groups.

Thus the simplest compound within this group is amino-' Instead of acids instance the mono-N-butyl amine salt of amine tetraacetic acid [CJH NHOOCCH (C H N (CH C-O OH It appears that the location within the molecule and size ethylene diof the alkyl chains in these compounds is not of great of high flexibility, elongation and edge tear and yet adequate tensile strength, and delamination resistance and wherein the appearance of the unified paper is not affected detrimentally.

It is an additional object of this invention toprovide a normally tacky and pressure-sensitive papertape having the aforementioned properties.

It is a further and more, specific object of'this invention to provide an impregnant compositionfor saturating paper webs to form backing elements with balanced properties of edge tear, flexibility, elongation, ten-f sile strength and delamination. resistance and wherein the appearance of the unified paper is not aifected detrimentally. 1 V

It is a further object of this invention to provide a novel method for producing unified paper web and norsoluble monodivalent salts such as mono calcium, mono lead, and mono zinc salts may be used.

Among preferredmaterials with this group arevany of the amine salts of the ethylene diamine polyacetic acids such as the diethyl amine salts and the butyl amine salts, and the univalent alkali metal salts of these acids,

such as the sodium, potassium and lithium salts. In like.

manner esters of the acids may also be used. The alkyl and alkylene chains in the moleculesmay be short as I in the case of the ethyl esters and ethyl amine salts or quite long as in the case of the octyl and diethylene esters and octyl amine salts. Chains of intermediate -PatentedMay 17,1960

their salts and esters may be used, for

3 length also serve satisfactorily; Di-, tri-, or tetra-acetates may be used in this invention and nitrilotriacetic acid and its esters and salts are well suited for its purposes. The preferred amino acetates cause little or no stains. on

sheet material of this invention, so long as the web is porous and can be completely saturated. The web may be made in part or in whole from wood, rope or rag fibers or other fibrous material, natural or synthetic.

Various types of fibrous webs may be employed as they materials which they contact. V 5 Preferably, paper webs of the conventional type em- The preferredv compounds to be used as protective ployed as backings for normally tacky and pressure-senagents with chloroprene polymers may be expressed by sitive adhesive tapes, such as those formed of kraft pulp the formula r and the like, are used. The paper may be flat or it may be creped, crimped, embossed or otherwise treated so as to provide rugosities or corrugations whereby stretch- N GHT COO D+ ability of the sheet is increased. R2 The preparation of polychloroprene from chloroprene wherein R is selected from the group consisting of -H, is f After slfitable PIIYifiQatiOH y careful and fractionation, chloroprene 1s emulsified in water by means of sodium rosinate soap and polymerized at 40 C. with (CH2)xNR3 CH2COO D+ the aid of potassium persulfate as a catalyst, and in the wherein R and R each are selected from the group presence of elemental sulfur as amodifier. A basic polyconsisting of H, CH CH OH, CH CO0--D+, merization recipe is as follows: and -CH COOR wherein R is an alkyl radical having Parts from two to five carbon atoms in the chain; wherein Chlorop 100 D is a cation selected from the group consisting of N d rosin 4 11+, Na+, K+, Li+, NH and NA H-H wherein A Sulfur 1 0.6 is at least one of the members of the group consisting of Water 150 hydrogen, alkyl and ethanol; and wherein x is at least So m hy roxi e 2 d t r tha 4, Sodium salt of naphthalene-sulfonic acid-form- It has been found that papers impregnated with a comaldehy e conde s tion Product 0.7 position containing a chloroprene polymer and any amino- Potassium pcrsulfatc 0.2-1.0 acetic acid of the aforementioned type exhibit satisfaclpiss lved in momma tory flexibility, tensile strength, elongation and delamination resistance for use as a backing for paper tapes. Moreover, chloroprene can be copolymcrized with Unified papers, produced in this manner, will not become relatively small amounts of other monomers. 'For exdiscolored or brittle on aging in contrast to paper unified ample, styrene comonomer tends to make a polychlorowith chloroprene polymers in the absence of the aminoprene with less crystallization tendencies, isoprene co acetic acid. Unified papers formed in accordance with monomer tends to make for better low-temperature servthis invention can be applied in sharp curve fashion ice,-and acrylonitrile for good processibility and oil rewithout tearing. Consequently, when used as a masking sistance. I a tape, the line of demarcation of paint is continuously Examples of suitable chloroprene (Z-chIoro-hutadiene) smooth so that no refinishing operations of the painted polymers useful in accordance with this invention are the surfaces are required. Moreover, the masking tapes of neoprene rubbers. Neoprene is a generic name applied this invention are of a high flexibility, so that they adhere 4 to polymers of chloroprene or mixtures of chloroprene to uneven or curved surfaces without difficulty. They and other polymerizable monomers; the major constituent exhibit no tendency to lift or curl easily, remaining of which is chloroprene. strongly adhered to the surfaces to which they are ap- Specific examples of neoprene latices are those manuplied so that there is no opportunity for paint to seep factured by the Du Pont Company, Wilmington, Delaunderneath the tape to destroy the purpose of said maskware, and sold under the trade names of Neoprene 571, ing tape. Neoprene-842A, Neoprene 601-A, Neoprene The exact mechanism, of the aminoacetic. acid in pre- 735 and "Neoprene 572. All of theselatices are alkaventing discoloration of the paper by aging of the chloline dispersions of polymerized chloroprene (2-chlororoprene polymer impregnant is not known. It does not I-S-butadiene) in water containing dispersing and stafunction as a mere acid acceptor, however, for ZnO bilizing'agents. Specific data for these'latices arezshown a commonly used acid acceptor gives an overall protecin the following Table I:

TABLE I Solids, Average Surface Particle chloroprene Percent Specific Initial Limiting Tension, Emulsltying Agent Diameter, Polymer By Gravity pH Viscosity, Dynes/cm. Microns Weight cps.

Neoprene 571 50 1. 10 12. 1 8.0 36 Sodium Roslnate 0. 13

Neoprene 842-15... 50 1.10 12.4 8.0 36 do 0.13

Neoprene 601A-... 59 1.12 12.2 35.0 42 ..do 0.13

Neoprene 735".-. 36 1. 08 12.2 6.0 36 Sodium Salt of Dls- 0.11

ropigrtlonated Neoprene 572. 50 1.10 12.2 8.0 as sodi u m Roslnatoun 0.13

tive action against discoloration far interior to that ob- In accordance with this invention, the fibrous web is tamed by using an amino-acetic acid. In like manner, impregnated with a chloroprene latex in amount sufiithe aminoacetic acid does not function as a mere anticient to enable incorporation of, the dry solids of. the oxidant, for the protective action etfected by it is far impregnant into the sheet in amount approximately v20 superior to that obtained by using Agerite White (dito 150%, and preferably 65' to 100% by weight of the B-naphthyl-p-phenylene diamine), a commonly used antidry non-impregnated sheet. In general, the aminoace oxidant for neoprene rubber products or 2,2, methylene tic acid is in an amount from about 0.2 to about. 10% bis (4 methyl-6-tert-butyl phenol), another commonly by weight of the chloroprene polymer. Amounts less recommendedneoprene antioxidant. than the indicated minimum range 0. do not always exert the desired protective actionagainst discolclosed for the purpose of comparison to highlight the novel features of the present invention. It should be noted that two temperatures, 200 and 250 F., were used for accelerated aging; 16 hours at 200? F. is a mild aging condition, 65 hours is a moderate aging condition.

whereas 182 hours at 200 For 16 hours at 250 F. is a severe aging condition.

Example I This example illustrates the production of a unified paper employing a chloroprene latex but containing no aminoacetic acid protective agent.

A 38-pound creped saturating paper was saturated with an equal dry weight of polychloroprene latex (Neoprene 735) having a Mooney viscosity of 68. The impregnation was accomplished with conventional squeeze roll equipment and the wet sheet dried in an air circulating oven at 250 F. The freshly impregnated sheet was light tan in color. When the same sheet was heat aged in an air circulating oven for merely 16 hours at 200 F. it turned dark brown and the paper was so brittle it tended to crumble. When heated 16 hours at 250 F., the paper turned brown-black and just crumbled.

Example II This example illustrates the production of a unified paper utilizing a latex comprising chloroprene and .a commonly used acid acceptor, namely, zinc oxide. A 27 pound creped saturating paper was saturated with 85% of its weight (dry basis) of a latex composition consisting of 90% polychloroprene (Mooney-60) and 10% of a dispersed zinc oxide. The freshly impregnated sheet was of a very light tan color and flexible. When heat aged for 65 hours at 200 F. it turned medium brown in color, became somewhat brittle. When heated 16 hours at 250 F. it turned dark brown in color, tended to crumble.

Example III at 200 F. the paper was still light in color and flexible. I When aged 16 hours at 250 F; no significant change in color was noted and the paper remained flexible.

Example IV This example illustrates the production of a unified paper utilizing a latex comprising polychloroprene and a commonly used neoprene antioxidant, namely 2,2- methylene bis (4-methyl-6-tert-butylphenol).

A 4-mil rope paper was saturated with 50% of its weight (dry basis) with a latex composition consisting of 97% polychloroprene (Mooney=45) and 3% 2,2- methylene bis (4-methyl-6-tert-butylphenol). The fresh:-

A 30 lb. flat kraft paper was satbrittle and crumbly.

6 1y impregnated sheet was light tanin color and flexible.

When aged 65 hours at 200 F. it turned slightly darker and was still flexible. When aged 182 hours at 200 F. for 16 hours at 250. F., it turned dark brown, became Example V This example illustrates. the production of a unified paper utilizing a latex comprising polychloroprene, a commonly used acid acceptor ZnO and a commonly used neoprene antioxidant 2,2 methylene bis (4-methyl-6- tert-butyl phenol).

A 4-mil rope paper was saturated with 75% of its weight (dry basis) with a latex'composition consisting of 87% polychloroprene (Mooney=45),-10% dispersed zinc oxide and 3% 2,2-methylene bis (4 -methyl-6-tertbutyl phenol). The freshly'impregnated sheet;was-very light tan in color and flexible. When aged 182 hours at 200 F. or 16 hours at 250 F. it turned dark brown in color and became stifi.

Example VI This example illustrates the production of a unified paper in accordance with this invention utilizing a latex comprising a polychloroprene, anaminoacetic acid (so dium salt of ethylene diamine-tetrawacetic acid) and an antioxidant 2,2 methylene-bis (4 methyl-6-tert-butylphenol).

A 4-milu'ope saturating paper was saturated with 50%.

of its weight (dry basis) with a latex composition con- I sisting of 95% polychloroprene (Mooney=45), 3% 2,2

. of2,2 methylene bis (4-methyl-6-tert-butylphenol). The,

methylene-bis (4-methyl-fi-tert-butylphenol) and 3% sodium salt of ethylene? diamine tetraacetic acid. I The freshly impregnated sheet was light in color and flexible.

When aged 182 hours at 200 F. or 16 hours at 250? F- it' turned light brown in color, but was considerably lighter in color than that of Example IV which used the antioxidant alone, and was lighter than that of Example V which used both an antioxidant and acid acceptor. The paper remained flexible.

Example ,VII

This is another example of a sheet unified inaccordance with this invention. This example is the same as in Example VI except that di-beta-napthyl paraphenylene diamine was used in place of 2,2 methylene bis (4- methyl- -6- tert-butyl-phenol). Again as in Example VII on naturally 'aging' the paper tended to turn pink. However, on heat aging,the samples remained lighter than those of Example VII.

. Example? The .same as in Example IV except that the antioxidant used washydroquinone monobenzyl ether in place fres'hly..impregnated .sheet was light tan in color but became brown under aging conditions of hours at 200 F.

' Example X This is another example in accordance "with the invention and is the same as in Example VI except that hydroquinone' monobenzyl ether is usedin; place of 2.2- methylene-bis (4-methyl 6-tert-butyl-phenol); Upon heat mama Example XI A 27-pound creped saturating paper was saturated with 85% of its weight (dry basis) of a latex composition consisting of 98% polychloroprene (Mooney=60) and 2%=of-the trisodium salt of ethylene diamine ethylol triacetic acid[C H N (CH CH OI-I) (CH COONa) Example XII A 70-pound fiat kraft paper was saturated with 25% of its weight (dry basis) of a latex composition consisting of 99% polychloroprene (Mooney=45) and 1% of the pentasodium salt of N,N,di(ethylamine diacetic acid) glycine-l (C H4 (CH COoNa) NCH COONa.

Example XIII A 4-mil rope saturating paper was saturated with 100% of its weight (dry basis) with a latex composition consisting of 88% polychloroprene (Money=45), 10% of the disodium lead salt of ethylene diamine tetraacetic acid -(CH COO) Pb(C H N (CH COONa) and 2% of a non-ionic salt such as Triton X-100 sold by Rohm & Haas, Philadelphia, Pennsylvania, the salt being necessary to stabilize the latex prior to addition of the antioxidant. The freshly impregnated sheet was light in color. When aged 16 hours at 250 F., the. sheet remained light in color and flexible.

As indicated heretofore, the unified papers formed in accordance with this invention are particularly useful as backings of normally tacky and pressure-sensitive tapes.

Any suitable normally tacky and pressure-sensitive adhesive useful in paper tapes may be used. Such adhesives are generally compounded from a composition of synthetic rubber or similar elastomeric polymer, and a resinous component compatible with the rubber and adapted to impart tack to the adhesive composition, together with suitable amounts of various types of additives such as conventional fillers, antioxidants, etc. The elastomeric component, tackifying resin, and fillers, when used; are proportioned to obtain in the adhesive properties of high internal strength and cohesiveness and high adhesiveness. As shown in the figure in cross-section, the adhesive tape comprises a unified backing having coated on one side a suitable normally tacky and pressuresensitive adhesive.

Examples of specific adhesive compositions useful in forming the novel tapes in accordance with this invention are as follows:

H TYPE A Milled pale crepe rubber 100 Polybetapinene resin Petroleum oil 5 Polymerized .trimethyldihydroquinoline 2 TYPE B Milled smoked sheet rubber 100 Zinc oxide 50 Dehydrogenated rosin 75 Sym. di+beta-napthyl-paraphenylene diamine 2 Lanolin TYPE 0 'Butadiene-styrene copolyrner (butadiene-styrene ratio 70:30 Mooney value 50) 50 Smoked sheet 50 Ester of hydrogenated rosin l 50 Polymerized trimethyldihydroquinoline 2 Petroleum oil' 20 I TYPE I) Polyvinyl ethyl ether resin intrinsic viscosity-2.37-.. Hydrogenated rosin 5- I Phenylalpha naphthylamine 0.35 j

Folyethylene glycol'400 (di, tri) ricinoleate 1.5-

7 TYPE E Y Polyisobutylene high polymer, solid ....7 100 Polyisobutylenepolymer, viscous liquid 70 Toluene 520 In forming the novel paper tapes of this invention,

the adhesive may be applied to the unified paper of the invention in any conventional manner, as for example by calendering, reverse roll-coater, knife-coater, etc. The adhesives are preferably applied to the unified paper from solvent solution or dispersion using aliphatic or aromatic solvents and subsequent drying. If desired, thebacking may be provided with a suitable conventional priming coating to improve the adherence of the coating thereto.

Preferably, the paper tapes of this invention are provided with a backsize composition on the side opposite the adhesively coated side of the unified backing. Also, if desired a release coating may be applied over the backsize coating, the backsize acting as a base coat in anchoring the release coating to the backing. The use of a release coating is particularly desirable wherein the delamination resistance is not as high as desired. Examples of suitable backsize composition for the above purpose are nitrocellulose, vinyl chloride-acetate copolymers and similar film formers.

The following is an example for the preparation ofa normally tacky and pressure-sensitive adhesive tape in,

accordance with the present invention:

Example X1 V crepe rubber adhesive Type A at a coating weight ofabout 1.5 ounces per sq. yd. of paper, drying the adhesive coating, and coating the opposite side of the paper with 0.3 ounce persquare yard of a nitrocellulose backsize composition.

The inventionin its broader aspects is not limited to the specific steps, compositions, combinations and improvements shown and described but departures may be made therefrom within the scope of the accompanying claims Without departing from the principles of the invention and Without sacrificing its chief advantages.

What is claimed is:

1. A paper-backed normally tacky and pressure-sensitive adhesive tape having satisfactory flexibility, elongation, edge tear resistance, delarnination resistance and resistance to discoloration comprising a unified paper sheet comprising a fibrous web internally bonded with a com position comprising a major amount of bonding particles including a chloroprene polymer and about 0.2 to 10% by weight of the chloroprene polymer of an aminoacetic acid compound of the formula wherein R is selected from the group consisting of --H, CH CH OH, ,CH COOD+, and --(CH )xNR CH COO-D-lwherein R and R each are selected from the group consisting of H, CH CH OH, -CH COO-D+, and -CH COOR wherein R is an 9 10 alkyl radical having from two to five carbon atoms in References Cited in the file of this patent the chain; wherein D is a cation selected from the UNITED STATES PATENTS group consisting of H+, Na+, K+, Li+, NH and NA H+, wherein A is at least one of the members of 2,287,063 Raynolfls June 1942- the group consisting of hydrogen, alkyl d ethylol and s 2,442,972 ln June 8, 1948 wherein x is at least 2 and not more than 4, said w 7 2,485,458 Q n Oct. 18, 1949 having at least one major surface'thereof coated with a 21492:702 Neubel't Dec. 27, 1949 normally tacky and pressure-sensitive dh i 2,560,743 enes July 17, 1951 2- A paper-backed normally tacky and pressure-sensi- 216971700 Dec. 21, 1954 tive adhesive tape in accordance with l im 1 wh i 10 2,751,365 June 19, 1956 the chloroprene polymer is in an amount f 20 t 150% 2,754,291 ollack July 10, 1956 by weight of the fibrous web. 2,765,228 Jordan" Oct. 2, 1956 3. A paper-backed normally tacky and pressure-sensb "2,765,229 MCI-3118111111 Oct. 2, 1956 ttve adhesive tape in accordance with claim 1 wherein the FOREIGN PATENTS aminoacetic acid compound is the sodium salt of ethylene l6 diamine tetraacetic acid. 551,113 Great Britain Feb. 8, 1943 IJ'NITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,937,109 May 17 1960 Charles Bartell .et a1 It is hereby certified that error appears in the printed specification of tlie' above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 66, for "interior" read inferior column 7, line 20, the fvormula should appear as shown below instead of as in the patent:

[C H N(CH COONa) NCH COONa Signed and sealed this 4th day of April 1961.,

(SEAL) new ERNEST w. SWIDER ZQQ XXX X I ARTHUR w. CROCKER estin Oflicer Acting Commissioner of Patents 

1. A PAPER-BACKED NORMALLY TACKY AND PRESSURE-SENSITIVE ADHESIVE TAPE HAVING SATISFACTORY FLEXIBLITY, ELONGATION EDGE TEAR RESISTANCE, DELAMINATION RESISTANCE AND RESISTANCE TO DISCOLORATION COMPRISING A UNIFIED PAPER SHEET COMPRISING A FIBROUS WEB INTERNALLY BONDED WITH A COMPOSITION COMPRISING A MAJOR AMOUNT OF BONDING PARTICLES INCLUDING A CHLOROPRENE POLYMER AND ABOUT 0.2 TO 10% BY WEIGHT OF THE CHLOROPRENE POLYMER OF AN AMINOACETIC ACID COMPOUND OF THE FORMULA 